Cannabis may further impair thinking speed and memory in people with MS who already have cognitive problems
About 20% of MS patients use cannabis, and preliminary evidence suggests smoked cannabis may worsen the processing speed and memory deficits that MS itself causes.
Quick Facts
What This Study Found
This review examined the sparse literature on cannabis effects on cognition in people with multiple sclerosis. About 20% of MS patients use cannabis for symptom relief or as a lifestyle choice. Since MS itself impairs cognition in many patients, the question of whether cannabis adds to that impairment is clinically important.
The limited evidence available suggested that smoked cannabis may further compromise information processing speed and memory in MS patients. Brain imaging (fMRI) showed more inefficient cerebral activation patterns during cognitive tasks in MS patients who use cannabis compared to those who do not.
Findings for pharmaceutical cannabis preparations (capsules or spray) were mixed and inconclusive. The authors emphasized that the evidence was preliminary due to methodological limitations and the small number of studies.
Key Numbers
About 20% of MS patients use cannabis. Smoked cannabis associated with slower processing speed and poorer memory. fMRI showed less efficient brain activation patterns. Pharmaceutical cannabis findings were equivocal.
How They Did This
Narrative review of existing literature on cannabis effects on cognition in MS patients, including both smoked cannabis and pharmaceutical preparations. Coverage included behavioral cognitive testing and fMRI brain imaging studies.
Why This Research Matters
MS patients face a difficult trade-off: cannabis may help with spasticity and pain but could worsen cognitive function. Without clear data, patients and clinicians are making decisions in the dark. This review highlights the urgent need for dedicated research.
The Bigger Picture
Cannabis is increasingly recommended or self-prescribed for MS symptoms, but its cognitive effects in a population already dealing with cognitive decline are poorly studied. This represents a significant gap in the evidence base for MS treatment guidelines.
What This Study Doesn't Tell Us
Very few studies available for review. Methodological limitations in existing research (small samples, cross-sectional designs, confounders). Cannot determine whether observed cognitive differences are caused by cannabis or reflect pre-existing differences between users and non-users.
Questions This Raises
- ?Does the form of cannabis (smoked vs. pharmaceutical) matter for cognitive effects in MS?
- ?Would lower-dose or CBD-dominant preparations avoid cognitive impairment?
- ?Do the cognitive costs outweigh the symptomatic benefits for individual patients?
Trust & Context
- Key Stat:
- ~20% of MS patients use cannabis; cognitive effects poorly studied
- Evidence Grade:
- Narrative review of a very small evidence base. Findings are preliminary and based on studies with methodological limitations.
- Study Age:
- Published in 2015. Research on cannabis and cognition in MS has expanded since.
- Original Title:
- What to make of cannabis and cognition in MS: In search of clarity amidst the haze.
- Published In:
- Multiple sclerosis (Houndmills, Basingstoke, England), 21(14), 1755-60 (2015)
- Authors:
- Feinstein, Anthony(8), Banwell, Emma(2), Pavisian, Bennis(4)
- Database ID:
- RTHC-00953
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
Does cannabis worsen thinking problems in MS?
Preliminary evidence suggests smoked cannabis may further impair processing speed and memory in MS patients. Brain imaging showed less efficient activation patterns. However, the evidence is limited and more research is needed.
Should MS patients avoid cannabis?
The review could not provide a definitive answer. Cannabis may help with spasticity and pain while potentially worsening cognition. The authors emphasized the need for more research to inform this clinical decision.
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Cite This Study
https://rethinkthc.com/research/RTHC-00953APA
Feinstein, Anthony; Banwell, Emma; Pavisian, Bennis. (2015). What to make of cannabis and cognition in MS: In search of clarity amidst the haze.. Multiple sclerosis (Houndmills, Basingstoke, England), 21(14), 1755-60. https://doi.org/10.1177/1352458515607652
MLA
Feinstein, Anthony, et al. "What to make of cannabis and cognition in MS: In search of clarity amidst the haze.." Multiple sclerosis (Houndmills, 2015. https://doi.org/10.1177/1352458515607652
RethinkTHC
RethinkTHC Research Database. "What to make of cannabis and cognition in MS: In search of c..." RTHC-00953. Retrieved from https://rethinkthc.com/research/feinstein-2015-what-to-make-of
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.